Scuba Deep Diving Safety Tips

Scuba Deep Diving Safety Tips

Scuba Deep Diving Safety Tips

“Plan your dive, dive your plan.” This is what the DM(Divemaster) will tell you. There’s nothing wrong with this rule, its just that when you are diving the site for the first time, discovery takes over. Your DM will tell you that the max depth is approximately 18m and approximately 1 hour. But once you are down there, you get distracted by your new discoveries. Sighting of hammer-head sharks down below is all it takes to get you deeper and deeper. We all know that hammer-head sharks don’t swim at 30m, it swims at 40m and deeper. So, what are you going to do? Go deeper! You go 35m below. You are too carried away by the sightings and suddenly you hear tank banging by your DM and he signals an ascend. You look at your gauges and WOW! 38m and half tank left. So, what are you going to do? Ascend is the only answer. Are we going for the 5m for 3 minutes safety stop? Is that enough? Theoretically, if you follow the RDP(Recreational Dive Planner), 5m for 3 minutes is sufficient. You can execute a 5m for 3 minutes safety stop but do you notice that you feel lethargic after that? I’m damn sure you do because the nitrogen is still in your body.

Whenever I find myself too carried away by the discoveries and ended up deeper than my dive plan, together with my dive buddy, we execute a different safety stop procedure. Instead of 5m for 3 minutes safety stop, we do a 3 minutes every 5m of ascend. What this means is that, if we are caught distracted at 38m below, we will abort all other activities and ascend 5m which is 33m and then swim and relax for 3 minutes and then proceed to ascend to the next 5m(28m) and stay for 3 minutes. We still swim around and take pictures during our 3 minutes. We repeat this until we hit the 5m for 3 minutes safety stop. I’m sorry to say that sometimes this take away most of the fun but what fun do you have if you are being forced to stop diving for the rest of the day. This method is much more safer as it releases more nitrogen out of your body and risk of decompression sickness is very much reduced.

I was taught this method while I was diving with a group of spear fishers. They go really deep and sometimes they defy all diving safeties. Be it surface interval, RDP or whatsoever. But they do use the method that I explained above. Once, I was diving with them and they went 38m below to spear fish. Once they got their catch, they will ascend 5m and scout the area and then ascend another 5m and repeat the ascend until they reach the surface. Once on board the boat, I ask them why. They gave me 2 explanation. One was the burst of the fish air bladder. The other was the tired feeling after the dive. They told me that, initially, they max their bottom time and do a 5m for 3 minutes safety stop. But they found out that the fish usually experience a burst air bladder and they feel tired for the rest of the day. There was this one dive that they had really good catch. They got the first fish at approximately 35m and the second at 30m and the third at 25m. They were so happy with the catch that they spend the rest of their dive scouting fish at different depth(which is shallower). Once on board the boat, they found that the fish didn’t had a burst air bladder. And they were feeling less tired. They did a research and found out that it is indeed safer to dive this way and you can log in more dives for one day. What happened? What went right? Here is the explanation.

Say, we are at 35m below and we inhale nitrogen. For the sake of discussion, we inhale 50 units of nitrogen. We went straight up to 5m and did a 5m for 3 minutes safety stop. How many units of nitrogen gets to escape? Not much. As we know, 50 units of nitrogen is equivalent to approximately 300 units of nitrogen at the surface. (air is compressed into ½ for every 10m of descend) So, a 5m safety stop for 3 minutes is not going to dispose a lot of nitrogen. Again for sake of discussion, let’s assume that 1minute at a shallower depth will dispose 10 units of nitrogen. At 5m for 3 minutes, we are going to dispose only 30 units of nitrogen but our body now has 300 units. So, we have 270 units of nitrogen in our body. How much surface time do you need to dispose of all the remaining 270 units of nitrogen? I bet it will take you some time and the more nitrogen residual in your body, the more tired you will feel. This also explains why the catch has a burst air bladder.

The second method which we use is the ascend 5m for 3 minutes and repeat until you reach the surface. This way, more nitrogen gets to escape your body. 50 units of nitrogen gets expanded to 75 units at 5m shallower. A 3 minutes stop will dispose 30 units of nitrogen and keeps 45 units of nitrogen. Another ascend will dispose another 30 units of nitrogen and so on(Table 1). For this discussion, we will be nitrogen free as we reach the surface but in reality, we still have some residual nitrogen in the body but that is very minimal and we don’t feel tired at all. That allows us to do another dive if we want to.

Depth

Residual Nitrogen

Nitrogen Dispose

Remaining Nitrogen

35m

50

30m

75

30

45

25m

67

30

37

20m

55

30

25

15m

37

30

7

10m

10

30

0

5m

0

N/A

N/A

This also explains why the catch didn’t have a burst air bladder. During the repeated ascends and stops, it gives time for the fish’s air bladder to dispose of air. Not only does this method disposes off nitrogen more efficiently but it also reduces the risk decompression sickness. A slow step by step ascend reduces air bubbles in your blood stream too. The air bubbles are being disposed of quicker than big bubbles are formed. It actually reduces the risk of decompression sickness efficiently.

I have been diving for some time and I have dive insurance too. But I wouldn’t want to risk being evacuated in a helicopter in the middle of my dive trip to a decompression chamber nearby. An experience I wouldn’t want to live and tell. Worst if you don’t have dive insurance.